1. Technical Field of the Invention
The present invention relates to a turbofan engine.
2. Description of Related Art
A turbojet engine of an aircraft having a bypass flow in the downstream of a fan for taking an air thereinto is called as “turbofan engine”. A bypass ratio corresponds to a flow rate ratio (bypass flow/core flow) between an air flow (a core flow) flowing into a core engine (a compressor, a combustor, and a turbine) and a bypass flow bypassing them. There is obtained an effect of reducing a flow speed of an exhaust jet and lowering a noise and a specific fuel consumption, in accordance with an increase of the ratio.
However, in the above-described turbofan engine, a problem arises in that a fan first-stage rotating blade (an up-front fan) and an inner diameter of a casing surrounding the fan first-stage rotating blade are enlarged by enlarging the bypass ratio, and a weight of the engine is increased.
In order to solve this problem, the inventors of the invention have proposed and filed a turbofan engine disclosed in Patent Document 1.
As shown in FIG. 1, the turbofan engine of Patent Document 1 is provided with a fan first-stage rotating blade 72 for taking an air thereinto and a spinner 74 for rotationally driving the fan first-stage rotating blade, in which the spinner includes a spiral blade 76 extending from an axis in a spiral shape in an outer-radial direction so as to suck an air from a front surface of the spinner and supply the air to the fan first-stage rotating blade.
[Patent Document 1]
Japanese Patent Application Laid-Open No. 2004-27854, “Turbofan Engine”
As described above, in the above-described turbofan engine, a problem arises in that the fan first-stage rotating blade (an up-front fan) and an inner diameter of a casing surrounding the fan first-stage rotating blade are enlarged by enlarging the bypass ratio, and a weight of the engine is increased.
In other words, as the fan first-stage rotating blade embedded into the spinner of the turbofan engine has an embedded structure, a certain degree of hub/tip ratio (inlet hub diameter/inlet tip diameter) is necessary, and an area of a fan inlet is narrowed as much as an area of the spinner.
Therefore, if it is intended to increase the bypass ratio for realizing a decrease in fuel consumption and noise, it is necessary to further widen the diameter of the fan and the inner diameter of the casing, so that the weight of the engine is increased.